Abstract
IntroductionTremor is a common side effect of treatment with lithium. Its characteristics can vary and when less rhythmical, distinction from myoclonus can be difficult.MethodsWe identified 8 patients on long-term treatment with lithium that developed upper limb tremor. All patients were assessed clinically and electrophysiologically, with jerk-locked averaging (JLA) and cross-correlation (CC) analysis, and five of them underwent brain MRI examination including spectroscopy (MRS) of the cerebellum.ResultsSeven patients (6 female) had action and postural myoclonus and one a regular postural and kinetic tremor that persisted at rest. Mean age at presentation was 58 years (range 42–77) after lengthy exposure to lithium (range 7–40 years). During routine monitoring all patients had lithium levels within the recommended therapeutic range (0.4-1 mmol/l). There was clinical and/or radiological evidence (on cerebellar MRS) of cerebellar dysfunction in 6 patients. JLA and/or CC suggested a cortical generator of the myoclonus in seven patients. All seven were on antidepressants and three additionally on neuroleptics, four of them had gluten sensitivity and two reported alcohol abuse.ConclusionsA synergistic effect of different factors appears to be contributing to the development of cortical myoclonus after chronic exposure to lithium. We hypothesise that the cerebellum is involved in the generation of cortical myoclonus in these cases and factors aetiologically linked to cerebellar pathology like gluten sensitivity and alcohol abuse may play a role in the development of myoclonus. Despite the very limited evidence in the literature, lithium induced cortical myoclonus may not be so rare.
Highlights
Tremor is a common side effect of treatment with lithium
Five of the patients included in this work have been referred to the Sheffield Ataxia Centre, Royal Hallamshire Hospital, Sheffield, UK because of balance problems while the remaining three cases were seen at a general neurology clinic primarily because of upper limb tremor
Four patients had ataxia on finger-nose and heel to sheen examination, evidence of gait ataxia and an irregular upper limb postural and action tremor that tended to persist at rest
Summary
Tremor is a common side effect of treatment with lithium. Its characteristics can vary and when less rhythmical, distinction from myoclonus can be difficult. Lithium induced tremor is a common side effect and can occur both early and after many years of exposure When manifesting early it usually consists of a fine tremor that can occur at rest, be postural and/or kinetic, often unrelated to blood levels [1,2,3,4,5,6,7,8,9,10]. Myoclonus is another movement disorder manifesting during treatment with lithium [11]. Shibasaki and Hallett make the argument that (2020) 6:5
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